This invention concerns liquid treatment, and more particularly liquid treatment apparatus using granular media such as deep bed filters or deionizers, the bed of granular media disposed in a tank through which is passed a liquid to be treated thereby.
In filters, the media must be cleaned periodically to remove accumulated filtered solids, as by backwashing the bed. This is also required in demineralizing apparatus where resin beads must be backwashed preparatory to brining the resin beads to reactivate the same. Backwashing can cause the loss of media if a too vigorous outflow is set up, but this limits the effectiveness of the cleaning of the media, which otherwise gradually becomes less effective.
U.S. Pat. No. 5,171,443 issued on Dec. 15, 1992 describes an improved regeneration process and system, particularly suited for filters using lightweight media such as crushed black walnut shells, but which is also applicable to deionizers. In that process and system the liquid and media are vigorously agitated to form a slurry, and the liquid and contaminants are caused to flow out through openings in a separator, the openings sized to block the escape of media granules.
In that process and system, the separator is a hollow cylindrical structure which is rotated within the slurry of liquid and media. The rotation of the separator prevents the media from clogging the separator strainer openings as the liquid flow draws the media against the openings, since the granules in suspension impact and dislodge the granules drawn against the separator openings.
This arrangement has worked very well and that design has been quite successful.
However, the need to rotate the separator necessitates the use of relatively costly seals, and also requires a significantly more powerful drive motor than that required to simply agitate the liquid, increasing the cost to manufacture and operate the apparatus.
It is the object of the present invention to provide a regeneration process and system for liquid treatment apparatus media which provides many of the advantages of the rotating separator design, but at a lower cost.